This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The effects of simian immunodeficiency virus (SIV) on blood-brain barrier permeability are likely initiated by glial response to the presence of virus in the central nervous system. This localized inflammatory reaction to the virus drives dysregulation of the endothelium by RNA modulation and protein phosphorylation. We examined interendothelial signaling by identifying and quantifying SIV-induced pro-inflammatory pathways and resultant message level changes in the endothelium, in response to SIV. We utilized confocal microscopy, cytokine multiplexing, RNA microarray, and RT-PCR. We determined a novel downregulation of CD263, a TNF decoy receptor in SIV stimulated endothelial cells, that normally serves to mitigate the damaging effects of TRAIL when the endothelium encounters an upsurge of proinflammatory stimuli. Supernatant from SIVmac251 infected macrophage was sufficient to cause astrocytes to overproduce TNF-[unreadable] by about 4-fold. Further, the same supernatant increased CCL2 and CXCL8 production in endothelial cells. We used RNA microarray to query RNA regulation in the macaque endothelium caused by SIVmac251 infection. These studies confirm that endothelial inflammation/activation is driven by pro-inflammatory cytokines, especially TNF-[unreadable]. The activation of the TNF-[unreadable] receptor in endothelial cells by its ligand causes activation of NF[unreadable]B in the endothelium. This leads to the subsequent upregulation/phosphorylation of MLCK, actin cytoskeletal reorganization, and redistribution of ZO-1. Displacement of ZO-1 leads to dysfunction of the endothelial tight junction possibly mediated through JAM-2 and claudin 8. We were able to largely mitigate changes in SIVmac251-driven mRNA changes in primary brain microvascular endothelial cells with inhibitors specific to MLCK and FAK.